Testing Bacteria Cultures from Different Sources


We'll grow bacteria into large cultures (multiple bacteria cells) to explore the different types of bacteria that live in our world.  Get ready to be grossed out!



Affiliate links to chemicals.

*Note: These chemicals can be purchased locally at stores such as Walmart/Target.

  • Erlenmeyer Flask

  • Mortar and pestle

  • Stirring rod

  • Petri dish

  • Nuffield Spatula

  • Optional: Additional dishes

  • Alcohol burner + stand + lighter


It is critical to be working in a sterile area with clean equipment.  Before you start, wash your hands very well and clean your Erlenmeyer flask.  Wash the stirring rod and spatula.

1. In mortar and pestle, crush bouillon and sugar.

2. In erlenmeyer flask, heat water and gelatin to boiling. Add bouillon and sugar to erlenmeyer and stir.

3. Remove from heat and let cool.

4. Pour into the petri dish (optional: make multiple cultures with additional dishes). Cover and place in the fridge overnight.

5. Use a cotton swab to collect samples.  Suggestions are from  your mouth, sponge, and toothbrush.

6. Take cotton swab and smear the sample on top of each dish.

7. Leave in a hot, humid place for 2-3 days.

The Science Behind the Reaction

There is SO much going on here.  First, did you see different types of mold growth based on the different swabs?  See this website for a great place to go and see what mold you grew.

Mold and bacteria are everywhere (and I mean, everywhere). But our eyes aren't able to detect such small specimens.  When we give the mold a place to grow and multiply, we are able to see it.

Much like the Crystal Snowflake concept!

Keep Experimenting!

There are so many places to take this experiment:

Does handwashing work better than sanitizer?

      Create 4 petri dishes. In each dish, add one sample:

       1. Your unwashed hand.

       2. Your "soap and water washed" hand.  Scrub   

         hands for about 20 seconds.

       3. Your "santized hand".  Use a lot!  

       4. Nothing, leave as basline comparison

Who is grosser?

      Create a petri dish for each member of your family.  Take a swab from each person's belly button.  

Is a dog's mouth really that clean?

     Test the theory that a dog's mouth is so clean you could have them lick a cut and it would clean it (eww).  Swab from your dogs mouth and your own, who wins?